1. Field of the Inventions
The present inventions relate to intake systems for supercharged engines.
2. Description of the Related Art
Supercharged engines are conventionally used in small boats and vehicles such as automobiles. Intake systems in such engines are generally adapted to supply the engine with air that is compressed by the supercharger, which is disposed in an intake passage. Some intake systems for supercharged engines are configured with a blow-off passage including a blow-off valve disposed in the intake passage. The blow-off passage and blow-off valve are generally configured to prevent an excessive increase in pressure within the intake passage. (See Japanese Patent Application JP-A-Hei 10-89079, for example).
In such intake systems for supercharged engines, a throttle valve is provided in the intake passage between the engine and the supercharger, and the blow-off passage connects the upstream side of the throttle valve and the upstream side of the supercharger. The blow-off valve, which is located in the blow-off passage, opens when the pressure on the upstream side of the throttle valve exceeds the pressure on the downstream side, and exceeds a predetermined value. When the blow-off valve opens, the air on the upstream side of the throttle valve, namely, the air between the throttle valve and the supercharger, returns to the upstream side of the supercharger through the blow-off passage. The blow-off valve and the blow-off passage thereby prevent damage to a compressor of the supercharger that could be caused by excessive pressure produced during abrupt deceleration.